This is hurting my head.
To remove my tank, I syphon as much fuel out of the tank as I can and then disconnect four lines before I even think about lifting the tank:
The two breather lines (push on plastic spigot things just below the upper subframe rail).
The two high pressure injection lines (above the right hand throttle body - hose clamps where they connect to the hard lines which go to the fuel distributor).
Then I faff around trying to get the pressurised residual fuel out of the high pressure lines without getting it all over the place (I've developed a technique involving a clamp and some wide hose leading to a fuel can - must get QD's one of these days).
Then I lift the tank and try to remove it.
Then I put it back down again and disconnect the brown earth lead from the fuel pump plate which I always forget
Then I lift the tank and remove it.
Seems simple to me